Tube amplifier assembly having a power tube and a capacitor assembly

ABSTRACT

Tube amplifier assembly including a power tube that is configured to be coupled to a grounding deck and positioned within an opening of the grounding deck. The tube amplifier assembly also includes a tube adapter that is configured to be coupled to the grounding deck. The tube adapter has a capacitive plate that extends parallel to the grounding deck and an adapter wall that is coupled to the capacitive plate. The tube adapter has an adapter opening that is aligned with the deck opening to form a tube passage. The tube adapter includes flexible conductive elements that are electrically coupled to the capacitive plate and surround the tube passage. The flexible conductive elements engage the power tube in the tube passage and electrically couple the power tube to the capacitive plate. The grounding deck and the capacitive plate form a capacitor assembly.

CROSS-REFERENCE TO RELATED APPLICATIONS

The subject matter set forth herein is similar to subject matterdescribed in U.S. application Ser. Nos. 14/575,885; 14/575,958; and14/575,993, which are filed on the same day as the present application.Each of the above applications is incorporated herein by reference inits entirety.

BACKGROUND

The subject matter herein relates generally to radio-frequency (RF)power generators and, more particularly, to RF power generators thatutilize power electron vacuum tubes.

Radioisotopes (also called radionuclides) have several applications inmedical therapy, imaging, and research, as well as other applicationsthat are not medically related. Systems that produce radioisotopestypically include a particle accelerator, such as a cyclotron, thataccelerates a beam of charged particles (e.g., H⁻ ions) and directs thebeam into a target material to generate the isotopes. The cyclotronincludes a particle source that provides the particles to a centralregion of an acceleration chamber. The cyclotron uses electrical andmagnetic fields to accelerate and guide the particles along apredetermined orbit within the acceleration chamber. The magnetic fieldsare provided by electromagnets and a magnet yoke that surrounds theacceleration chamber. The electrical fields are generated by a pair ofradio frequency (RF) electrodes (or dees) that are located within theacceleration chamber. The RF electrodes are electrically coupled to anRF power generator that may include, for example, oscillators,amplifiers, control circuitry, and power supplies. The RF powergenerator energizes the RF electrodes to provide the electrical field.The electrical and magnetic fields within the acceleration chamber causethe particles to take a spiral-like orbit that has an increasing radius.When the particles reach an outer portion of the orbit, the particlesare directed toward the target material for radioisotope production. Inaddition to controlling the orbit of the particles, the RF electrodesmay be used to pull the particles from a particle source in theacceleration chamber.

To operate the RF electrodes within the acceleration chamber, aconsiderable amount of electric power (e.g., 5 kW to 2 MW) is generatedby the RF power generator and delivered to the RF electrodes. The powergenerator includes, among other things, a tube amplifier unit having apower electron vacuum tube (or power tube). The power tube is typicallymounted to a grounding deck that separates a cathode cavity and an anodecavity. The power tube may be, for example, a power triode having acathode, anode, and control grid. In a power triode, the cathode isheated by a filament that receives current from a power supply. Theheated filament causes the cathode to emit electrons, which flow throughthe vacuum tube toward the anode. The control grid is positioned betweenthe cathode and anode and may be used to control the flow of theelectrons. Other power tubes utilized by power generators may include atetrode and a pentode.

A socket is often used to mechanically and electrically couple the powertube to the grounding deck. The socket, however, can be expensive andcan limit the options available for controlling the electricalperformance of the RF amplification system. An alternative to the socketconnection includes using flexible leads (also called flying leads) thatare electrically coupled to the filament and are used to heat thefilament during operation of the power tube. It can be a challenge,however, to connect the power tube to the grounding deck without asocket and be capable of operating within the very high frequency (VHF)band or higher while achieving a designated efficiency. For example, itis not recommended to operate power tubes with flexible leads at 100 MHzand above. Moreover, it may be desirable to monitor signals at thecathode resonator to control electrical performance. Socket-mountedpower tubes, however, may require that a separate device be installedfor monitoring the signals.

BRIEF DESCRIPTION

In an embodiment, a tube amplifier assembly is provided that includes agrounding deck having an anode side and a cathode side that face inopposite directions. The grounding deck has a deck opening therethroughthat extends transverse to a central axis. The tube amplifier assemblyalso includes a power tube that is coupled to the grounding deck andpositioned within the deck opening. The tube amplifier assembly alsoincludes a tube adapter coupled to the grounding deck and positionedalong the cathode side. The tube adapter has a capacitive plate thatextends parallel to the grounding deck and an adapter wall that iscoupled to the capacitive plate. The tube adapter has an adapter openingthat is aligned with the deck opening to form a tube passage. The tubeadapter includes flexible conductive elements that are electricallycoupled to the capacitive plate and surround the tube passage. Theflexible conductive elements engage the power tube in the tube passageand electrically couple the power tube to the capacitive plate. Thegrounding deck and the capacitive plate form a capacitor assembly of thetube amplifier assembly.

In an embodiment, a tube amplifier assembly is provided that includes agrounding deck having an anode side and a cathode side that face inopposite directions. The grounding deck having a deck openingtherethrough. The tube amplifier assembly also includes a capacitiveplate extending parallel to the grounding deck and an interposed plateextending parallel to and positioned between the grounding deck and thecapacitive plate. The interposed plate is electrically separated fromthe grounding deck and the capacitive plate. The capacitive plate has aplate opening and the interposed plate has a plate opening that arealigned with the deck opening to form a tube passage. The tube amplifierassembly also includes a power tube positioned within the tube passageand electrically coupled to the capacitive plate. The interposed plate,the capacitive plate, and the grounding deck form a capacitor assemblythat is configured to provide capacitance of the tube amplifierassembly.

In an embodiment, a capacitor assembly is provided that includes acapacitive plate configured to extend parallel to and be coupled to agrounding deck of a tube amplifier assembly. The capacitive plate has aplate opening that extends transverse to a central axis. The capacitorassembly also includes an adapter wall mechanically coupled to thecapacitive plate. The adapter wall has an inner surface that surroundsthe central axis and defines a tube opening. The plate opening and tubeopening combine to form a tube passage that is sized and shaped toreceive a power tube of the tube amplifier assembly. The capacitorassembly also includes flexible conductive elements that are distributedalong the inner surface of the adapter wall. The flexible conductiveelements are configured to engage the power tube in the tube passage andelectrically couple the power tube to the capacitive plate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an isotope production system inaccordance with an embodiment.

FIG. 2 illustrates a perspective view of the isotope production systemof FIG. 1 having a cyclotron that is opened to illustrate components ofthe cyclotron.

FIG. 3 is a perspective view of a radio frequency (RF) power generatorhaving a tube amplifier assembly in accordance with an embodiment.

FIG. 4 is a partially exploded view of a movable tray assembly formed inaccordance with an embodiment.

FIG. 5 is a side view of a power tube that may be used with the tubeamplifier assembly of FIG. 3.

FIG. 6 illustrates an exemplary clamp section that may be used with thetube amplifier assembly of FIG. 3.

FIG. 7 is a plan view of a clamp ring that may be used with the tubeamplifier assembly of FIG. 3.

FIG. 8 is a perspective view of a portion of the tube amplifier assemblyof FIG. 3.

FIG. 9 is an exploded view of a capacitor assembly that may be used withthe tube amplifier assembly of FIG. 3.

FIG. 10 is a plan view of an insulation layer that may be used with thetube amplifier assembly of FIG. 3.

FIG. 11 is a plan view of an interposed plate that may be used with thetube amplifier assembly of FIG. 3.

FIG. 12 is an isolated perspective view of a tube adapter that may beused with the tube amplifier assembly of FIG. 3.

FIG. 13 is a cross-section of the tube adapter of FIG. 12.

FIG. 14 is a cross-section of an input circuit of the tube amplifierassembly illustrating the capacitor assembly in greater detail.

FIG. 15 illustrates a side view of an input circuit of the tubeamplifier assembly showing a communication line that is coupled to theinterposed plate.

DETAILED DESCRIPTION

The following detailed description of certain embodiments will be betterunderstood when read in conjunction with the appended drawings. To theextent that the figures illustrate diagrams of the functional blocks ofvarious embodiments, the functional blocks are not necessarilyindicative of the division between hardware circuitry. For example, oneor more of the functional blocks (e.g., processors or memories) may beimplemented in a single piece of hardware (e.g., a general purposesignal processor or a block of random access memory, hard disk, or thelike) or multiple pieces of hardware. Similarly, the programs may bestand alone programs, may be incorporated as subroutines in an operatingsystem, may be functions in an installed software package, and the like.It should be understood that the various embodiments are not limited tothe arrangements and instrumentality shown in the drawings.

As used herein, an element or step recited in the singular and proceededwith the word “a” or “an” should be understood as not excluding pluralof said elements or steps, unless such exclusion is explicitly stated,such as by stating “only a single” element or step. Furthermore,references to “one embodiment” are not intended to be interpreted asexcluding the existence of additional embodiments that also incorporatethe recited features. Moreover, unless explicitly stated to thecontrary, embodiments “comprising” or “having” an element or a pluralityof elements having a particular property may include additional suchelements not having that property.

Embodiments set forth herein include radio-frequency (RF) powergenerators and tube amplifier assemblies that include a power tube andat least one cavity resonator coupled to the power tube. The cavityresonators may include input and output cavity resonators (or cathodeand anode cavity resonators, respectively) that may be, for example,coaxial transmission line resonators that each include an innerconductor and an outer conductor. The input and output cavity resonatorsmay be characterized as high-Q resonators that are configured to operateat a designated frequency, such as within the very high frequency (VHF)band or higher (e.g., at least 30 MHz). As one example, the designatedfrequency may be 100 MHz. The input and output resonators may be ¼wavelength resonators (or λ/4 resonators). In particular embodiments,embodiments have a grounded-grid configuration such that the power tubeis cathode-driven and has a control grid that is operated at RF ground.

In some embodiments, the power tube is a triode having a grounded gridconfiguration. In particular embodiments, the power tube does notinclude and is not connected to a conventional socket. The power tubemay include flexible leads (also referred to as flying leads).Embodiments may also include capacitor assemblies that are configuredadd capacitance to corresponding cavity resonators.

Although the RF power generators and the tube amplifier assembliesdescribed herein are used to supply power to a particle accelerator, itshould be understood that the RF power generators and tube amplifierassemblies may be used in other applications. In particular embodiments,the RF power generators or tube amplifier assemblies may be high powersystems that are capable of generating, for example, 1,000 W or more and500 V or more.

A technical effect provided by one or more embodiments may include amechanism for increasing capacitance of a tube amplifier assembly or,more specifically, a cavity resonator of the tube amplifier assemblythat includes a power tube. The added capacitance may increase anefficiency of the tube amplifier assembly, reduce power consumption ofthe tube amplifier assembly, and/or reduce overall cost of the tubeamplifier assembly. In some cases, the added capacitance may increasethe resonance Q-value and thereby reduce distortion. Another technicaleffect may include a mechanism for monitoring signals at the cathode ofthe power tube. In particular, embodiments may monitor a waveform of thesignals at the cathode to calculate a phase difference of the signal atthe cathode relative to a monitored signal at the anode of the powertube. The phase may provide information regarding an amplifier load. Bymonitoring the phase difference or waveform of the signals, theRF-frequency may be controlled (e.g., within 1% of an operatingfrequency, such as about 100 MHz) to control a load condition, which mayaffect total system efficiency by reducing losses. Another technicaleffect may include a mechanism for holding the power tube and/or cathoderesonator (or inner conductor) at a designated position relative toother components. Another technical effect may include an assemblyprocess that reduces manufacturing tolerances and/or an assembly processthat is simpler than know processes. Another technical effect mayinclude the ability to operate power tubes with flexible leads (orflying leads) at 100 MHz or higher. Although the above provides examplesof technical effects that may be provided by embodiments set forthherein, it should be understood that embodiments are not required toprovide each of the technical effects. For instance, one or moreembodiments may achieve only one of the technical effects.

FIG. 1 is a perspective view of an isotope production system 100 inaccordance with an embodiment. The isotope production system 100includes a particle accelerator 102 that is operably coupled to acontrol cabinet 104 and a RF power generator 106. In the illustratedembodiment, the particle accelerator 102 is an isochronous cyclotron,but other types of particle accelerators may be used. RF energy or poweris supplied to the particle accelerator 102 through an RF cable 105. Asshown, the particle accelerator 102 includes a magnet assembly 108 thatincludes yoke sections 111, 112 and electromagnets 113, 114 that arecoupled to the yoke sections 111, 112, respectively.

FIG. 2 is a perspective view of a portion of the particle accelerator102. Although the following description is with respect to the particleaccelerator 102 being a cyclotron, it is understood that embodiments mayinclude other particle accelerators and sub-systems of the same. Asshown in FIG. 2, the particle accelerator 102 includes the magnetassembly 108 having the yoke sections 111, 112 and the electromagnets113, 114. The electromagnets 113, 114 are magnet coils in theillustrated embodiment. The particle accelerator 102 may also includepole tops 116, 118. The pole top 116 is secured to the yoke section 111,and the pole top 118 is secured to the yoke section 112. As shown, theyoke section 112 is rotatably coupled to the yoke section 111. Duringoperation, the yoke section 112 is in a closed position (as shown inFIG. 1) such that the pole tops 116, 118 oppose each other and anacceleration chamber is defined therebetween. When the particleaccelerator 102 is not operating, the yoke section 112 may be opened toallow access to the acceleration chamber.

The acceleration chamber is configured to allow charged particles, suchas ¹H⁻ ions, to be accelerated therein along a predetermined curved paththat wraps in a spiral manner about an axis that extends between centersof the opposing pole tops 116, 118. The charged particles are initiallypositioned proximate to a central region 120 of the accelerationchamber. When the particle accelerator 102 is activated, the path of thecharged particles may orbit around the axis that extends between thepole tops 116, 118. In particular embodiments, the pole top 118 includeshills 122 and valleys 124. The particle accelerator 102 also includes apair of RF electrodes 126, 128 that are positioned adjacent to the poletop 116. The RF electrodes 126, 128 are sized and shaped to be receivedwithin corresponding valleys 124 of the pole tope 118 when the yokesection 112 is closed.

The RF electrodes 126, 128 are configured to be energized by the RFpower generator 106 (FIG. 1) to generate an electrical field. Themagnetic field is provided by the yoke sections 111, 112 and theelectromagnets 113, 114. When the electromagnets 113, 114 are activated,a magnetic flux may flow between the pole tops 116, 118 and through theyoke sections 111, 112 around the acceleration chamber. When theelectrical field is combined with the magnetic field, the particleaccelerator 102 may direct the particles along the predetermined orbit.The RF electrodes 126, 128 cooperate with each other and form a resonantsystem that includes inductive and capacitive elements tuned to apredetermined frequency (e.g., 100 MHz). Accordingly, the RF electrodes126, 128 are controlled by the RF power generator 106 to accelerate thecharged particles.

In particular embodiments, the system 100 uses ¹H⁻ technology and bringsthe charged particles (negative hydrogen ions) to a designated energywith a designated beam current. In such embodiments, the negativehydrogen ions are accelerated and guided through the particleaccelerator 102. The negative hydrogen ions may then hit a strippingfoil (not shown) such that a pair of electrons are removed and apositive ion, ¹H⁺ is formed. The positive ion may be directed into anextraction system (not shown). However, embodiments described herein maybe applicable to other types of particle accelerators and cyclotrons.For example, in alternative embodiments, the charged particles may bepositive ions, such as ¹H⁺, ²H⁺, and ³He⁺. In such alternativeembodiments, the extraction system may include an electrostaticdeflector that creates an electric field that guides the particle beamtoward the target material.

The system 100 is configured to produce radioisotopes (also calledradionuclides) that may be used in medical imaging, research, andtherapy, but also for other applications that are not medically related,such as scientific research or analysis. When used for medical purposes,such as in Nuclear Medicine (NM) imaging or Positron Emission Tomography(PET) imaging, the radioisotopes may also be called tracers. By way ofexample, the system 100 may generate protons to make ¹⁸F⁻ isotopes inliquid form, ¹¹C isotopes as CO₂, and ¹³N isotopes as NH₃. The targetmaterial used to make these isotopes may be enriched ¹⁸O water, natural¹⁴N₂ gas, ¹⁶O-water. In some embodiments, the system 100 may alsogenerate protons or deuterons in order to produce ¹⁵O gases (oxygen,carbon dioxide, and carbon monoxide) and ¹⁵O labeled water.

The system 100 may also be configured to accelerate the chargedparticles to a predetermined energy level. For example, some embodimentsdescribed herein accelerate the charged particles to an energy ofapproximately 18 MeV or less. In other embodiments, the system 100accelerates the charged particles to an energy of approximately 16.5 MeVor less. In particular embodiments, the system 100 accelerates thecharged particles to an energy of approximately 9.6 MeV or less. In moreparticular embodiments, the system 100 accelerates the charged particlesto an energy of approximately 7.8 MeV or less. However, embodimentsdescribe herein may also have an energy above 18 MeV. For example,embodiments may have an energy above 100 MeV, 500 MeV or more. Likewise,embodiments may utilize various beam current values. By way of example,the beam current may be between about of approximately 10-30 μA. Inother embodiments, the beam current may be above 30 μA, above 50 μA, orabove 70 μA. Yet in other embodiments, the beam current may be above 100μA, above 150 μA, or above 200 μA.

FIG. 3 is a perspective view of a RF power generator 130, which may beused with an isotope production system, such as the isotope productionsystem 100 (FIG. 1). It is contemplated, however, that the RF powergenerator 130 may be used in other applications that require RF poweramplification. The RF power generator 130 may be similar to the RF powergenerator 106 (FIG. 1) and configured to energize RF electrodes, such asthe RF electrodes 126, 128 (FIG. 2). The RF power generator 130 includesa generator housing 132, which may be referred to as a cabinet in someembodiments. The generator housing 132 houses a number of interconnectedcomponents of the RF power generator 130 that cooperate in generating asufficient amount of electric power for operating the RF electrodes.

The generator housing 132 defines a housing cavity 134 that may bedivided or apportioned by interior walls to form compartments 135-140.The generator housing 132 may include an outer enclosure 133 havingexternal walls 141-145. In some embodiments, the external walls 141-145face an exterior space that is readily accessible to individuals and/orthat has equipment positioned adjacent to one or more of the externalwalls 141-145. As such, the generator housing 132 and other internalshielding structures may be configured to obtain a designatedelectromagnetic compliance (EMC). More specifically, the generatorhousing 132 may be configured to reduce leakage of electromagneticenergy into the exterior space. Embodiments configured to obtain adesignated FMC are described in U.S. patent application Ser. No.14/575,958, which is incorporated herein by reference in its entirety.

As shown, the RF power generator 130 is oriented with respect tomutually perpendicular axes, including a longitudinal axis 191, alateral axis 193, and a depth axis 197. The lateral axis 193 extendslaterally between the external walls 142, 144. The longitudinal axis 191may be a vertical axis that extends parallel to the force of gravity,and the depth axis 197 may extend into the housing cavity 134. It iscontemplated that the longitudinal axis 191 in other embodiments may notextend parallel to the force of gravity.

The generator housing 132 includes a conductive frame 256 that surroundsand defines openings to the compartments 135-139. The conductive frame256 may include, for example, flexible conductive elements 257 (e.g.,contact springs, spring fingers, and the like) that are configured toengage an access panel (not shown). The compartments 137-139collectively form an interior space 155 that is configured to receive atleast a majority of the primary components of a tube amplifier assembly170. As described herein, the tube amplifier assembly 170 includes amovable tray assembly 165 that may include a plurality of interconnectedcomponents of the tube amplifier assembly 170.

The movable tray assembly 165 allows for the components to be assembled,serviced, and/or tested outside of the interior space 155 and thenmoved, as a unit, into the interior space 155. The movable tray assembly165 may divide the interior space 155 into the compartments 137-139 whenthe movable tray assembly 165 is operably positioned within the interiorspace 155. Moreover, the movable tray assembly 165 may be movable todifferent levels along the longitudinal axis 191. Moving the movabletray assembly 165 along the longitudinal axis 191 may effectively changea length of one or more resonators of the tube amplifier assembly 170.As such, moving the movable tray assembly along the longitudinal axis191 may be referred to as coarse tuning the tube amplifier assembly 170.The movable tray assembly 165 is described in greater detail in U.S.application Ser. No. 14/575,993, which is incorporated herein byreference in its entirety. The generator housing 132 may also have anhousing door (not shown) that provides general access to the housingcavity 134 and may cover the housing cavity 134 during operation of theRF power generator 130.

The compartment 137 may be hereinafter referred to as an output cavity137, and the compartment 138 may be hereinafter referred to as a inputcavity 138. The compartments 135-140 may be defined by interiorconductor walls that are positioned within the housing cavity 134. Forexample, the interior conductor walls include a grounding deck 146 and ashorting deck 148. The grounding deck 146 is part of the movable trayassembly 165 and separates the output and input cavities 137, 138. Thegrounding deck 146 may have an input side that faces the input cavity138 and an output side that faces the output cavity 137. One or more ofthe conductor walls may include apertures 150 that permit air to flowtherethrough. For example, the RF power generator 130 may include athermal control unit 152 (e.g., air cooling unit) that circulates airwithin the housing cavity 134.

Operative components of the RF power generator 130 that are disposedwithin the output cavity 137 may include an output inner conductor 154,a tuning capacitor assembly 204, and a power tube 158. The output cavity137 may also include an output coupling loop (or pickup loop) 160therein. The input cavity 138 may be at least partially defined by aconductor sub assembly 164 and include an input inner conductor 162therein. A portion of the power tube 158 may extend within the inputcavity 138. In the illustrated embodiment, the conductor sub-assembly164 is U-shaped and secured to the grounding deck 146. The groundingdeck 146 and the conductor sub-assembly 164 may collectively form asupport frame 168 of the movable tray assembly 165. As shown, the RFpower generator 130 also includes multi-layered decoupling capacitors200 that are secured to the conductor sub-assembly 164. The decouplingcapacitors 200 are described in U.S. application Ser. No. 14/575,885,which is incorporated herein by reference in its entirety.

In some embodiments, the grounding deck 146, the power tube 158, theinput inner conductor 162, the conductor sub-assembly 164, and/or thetuning capacitor assembly 204 may form the movable tray assembly 165.The movable tray assembly 165 may be secured to the output innerconductor 154, the decoupling capacitors 200, cooling tubes (not shown),and a supply cable (not shown) to form the tube amplifier assembly 170.In an exemplary embodiment, the tube amplifier assembly 170 includes thesupport frame 168, the power tube 158, the tuning capacitor assembly204, the decoupling capacitors 200, the input inner conductor 162, theoutput inner conductor 154, the coupling loop 160, and outer conductorsformed by the RF power generator 130. The tube amplifier assembly 170may include fewer or more components in other embodiments. In theillustrated embodiment, the tube amplifier assembly 170 includes aninput cavity resonator 390 (FIG. 15) that is formed by the input innerconductor 162, an input outer conductor (not shown), and a cavitycapacitor assembly 250.

FIG. 4 is a partially exploded view of the movable tray assembly 165 inaccordance with an embodiment. It should be understood that FIG. 4 andthe accompanying description illustrate just one example of a movabletray assembly and that other embodiments may be assembled in accordancewith the teachings herein. As shown in FIG. 4, the grounding deck 146and the conductor sub-assembly 164 have been separated. The movable trayassembly 165 may include the input inner conductor 162 and a capacitorassembly 250. The capacitor assembly 250 is described below and may beused to couple the input inner conductor 162 to the grounding deck 146.

The conductor sub-assembly 164 may include a plurality of ground walls171-173. In the illustrated embodiment, the ground walls 171-173 form aU-shaped structure, but other shapes may be formed by the ground walls171-173. The ground wall 172 extends between and joins the ground walls171, 173 and includes a plurality of the apertures 150 for airflow. Theground walls 171, 173 may project away from the input side of thegrounding deck 146. The ground wall 172 is configured to electricallycouple to the input inner conductor 162. The ground walls 171, 173 mayinclude coupling edges 174, 176, respectively, that are configured toelectrically couple to the grounding deck 146. For example, the groundwalls 171, 173 may include conductive elements 178 along the couplingedges 174, 176.

Also shown in FIG. 4, the conductor sub-assembly 164 may include a frontgrounding panel 180 and a rear grounding panel 182 that each include aplurality of flexible conductive elements 184. For example, conductiveelements may include elongated bodies (e.g., beams) that are configuredto resiliently flex when engaging another component. When engaged toanother component, the conductive elements may have a stored energy thatcontinuously biases the conductive element against the other componentso that the conductive elements contact and remain engaged to the othercomponent during operation of the RF power generator 130 (FIG. 3).

The grounding deck 146 includes a base plate 186, a pair of sidewalls187, 188, and a pair of structure supports 189, 190. The base plate 186includes flexible conductive elements 192 positioned along a front endthat are configured to engage the access panel (not shown). Thegrounding deck 146 may also include conductive elements (not shown)along a back end that are configured to engage an interior surface ofthe generator housing 132. Likewise, the sidewall 188 may includeconductive elements 194 positioned therealong that are configured toengage an interior surface of the generator housing 132. The sidewall187 may also include conductive elements 194 (shown in FIG. 5)positioned therealong for engaging another interior surface of thegenerator housing 132.

The structure supports 189, 190 are secured to the base plate 186 andare configured to couple to the ground walls 171, 173, respectively. Theconductive elements 178 may engage the structure supports 189, 190. Thestructure supports 189, 190 may be L-shaped. In an exemplary embodiment,the conductor sub-assembly 164 is capable of being positioned atdifferent distances with respect to the grounding deck 146. For example,the movable tray assembly 165 includes hardware 246 (e.g., screws, nuts,bolts, washers, etc.) and slots 248 that receive the hardware 246. Thehardware 246 is used to secure the ground walls 171, 173 to thestructure supports 189, 190, respectively. The ground walls 171, 173include corresponding holes that receive the hardware 246. As shown, theslots 248 extend lengthwise along the longitudinal axis 191. The slots248 permit the conductor sub-assembly 164 to be positioned at differentdistances relative to the grounding deck 146. In particular, theshorting deck 148 may be positioned at different distances with respectto the grounding deck 146 to change a length of the input cavity 138(FIG. 3).

Accordingly, the support frame 168 may provide conductive paths thatextend from the ground walls 171, 173 to one or more of the conductiveelements 184, 192, and 194 and, consequently, to the generator housing132. The ground walls 171, 173 may be configured to electrically groundthe decoupling capacitors 200. Moreover, the ground walls 171, 173 mayform part of the outer conductor (not shown) of the input resonator 390(FIG. 15).

The support frame 168 may include blocking tabs 196 that extendlaterally away from the sidewalls 187, 188. Returning to FIG. 3, whenthe movable tray assembly 165 is positioned within the interior space155, the movable tray assembly 165 is positioned between opposing ledgesupports 198 of the generator housing 132. For example, the groundingdeck 146 may extend between and be electrically coupled to innersurfaces of the ledge supports 198. During the positioning process, themovable tray assembly 165 may be initially positioned above the ledgesupports 198 and then lowered, in a direction along, the longitudinalaxis 191 such that a portion of the movable tray assembly 165 extendsbetween the ledges supports 198. The blocking tabs 196 may be configuredto prevent the movable tray assembly 165 from moving completely throughthe opening between the ledge supports 198. In alternative embodiments,the blocking tabs 196 may not be used and, instead, the ledge supports198 may include tabs that prevent the movable tray assembly 165 frommoving completely through the opening between the ledge supports 198.The movable tray assembly 165 is described in greater detail in U.S.application Ser. No. 14/575,993, is incorporated herein by reference inits entirety.

FIG. 5 is a side view of the power tube 158. In an exemplary embodiment,the power tube 158 is a power triode that includes a tube body 210 thatis coupled to flexible leads 218, 220. The tube body 210 encloses acathode, anode, and control grid (not shown) of the power tube 158. Thepower tube 158 also includes a cathode terminal 212, an anode terminal214, and a grid terminal 216 that are each coupled to and supported bythe tube body 210. The grid terminal 216 is a grid collar in theillustrated embodiment. The cathode terminal 212 is electrically coupledto the cathode electrode, the anode terminal 214 is electrically coupledto the anode electrode, and the grid terminal 216 is electricallycoupled to the control grid.

In the illustrated embodiment, the power tube 158 also includes flexibleleads 218, 220 that are electrically coupled to a filament within thetube body 210. The cathode may be heated by the filament, which receivescurrent from the flexible lead 218. The heated filament causes thecathode to emit electrons, which flow through the power tube 158 towardthe anode. The control grid is positioned between the cathode and anodeand may be used to control the flow of the electrons. Although someembodiments may include a power tube having flexible or flying leads, itis contemplated that other embodiments may include a power tube thatincludes or is coupled to a conventional socket. Moreover, although thepower tube 158 is a power triode in some embodiments, it should beunderstood that other power tubes may be used, such as tetrodes orpentodes.

As shown, the cathode terminal 212 has an terminal diameter 213, theanode terminal 214 has an terminal diameter 215, and the grid terminal216 has a grid diameter 217. The grid diameter 217 may be greater thanthe terminal diameter 213 of the cathode terminal 212 and smaller thanthe terminal diameter 215 of the anode terminal 214.

FIG. 6 is a plan view of a clamp section 222 that is configured tocouple the power tube 158 (FIG. 3) to the grounding deck 146 (FIG. 3).In an exemplary embodiment, the clamp section 222 is combined withanother clamp section 222 and configured to hold the grid terminal 216(FIG. 5) against the base plate 186 (FIG. 3). In the illustratedembodiment, the clamp section 222 is C-shaped or semi-circular, but itshould be understood that other shapes may be used. The clamp section222 includes an inner edge 224 and an outer edge 226. The inner edge 224has a radius that is less than the radius of the grid terminal 216, andthe outer edge 226 has a radius that is greater than the radius of thegrid terminal 216. The clamp section 222 also includes thru-holes 228that are configured to receive hardware 242 (e.g., screws, nuts, bolts,washers, etc.) for securing the clamp section 222 to the grounding deck146.

FIG. 7 is a plan view of a clamp ring 230. The clamp ring 230 isconfigured to be positioned between two of the clamp sections 222 (FIG.6) and the grounding deck 146 (FIG. 3) or, more specifically, the baseplate 186 (FIG. 3) of the grounding deck 146. The clamp ring 230 has aninner edge 231 and an outer edge 232 that are sized and shaped relativeto the clamp section 222. The inner edge 231 has a radius that isgreater than the radius of the grid terminal 216. The clamp ring 230 isconfigured to separate the clamp sections 222 from the base plate 186.In the illustrated embodiment, the clamp ring 230 is configured toextend alongside the outer edges 224 of the clamp sections 222. As such,the clamp ring 230 may have a ring diameter 234 that is approximatelyequal to or slightly less than a clamp diameter (not shown) formed bythe two clamp sections 222.

FIG. 8 is a perspective view of an anode portion of the tube amplifierassembly 170. The tube amplifier assembly 170 may include a mountingassembly 240 that couples the power tube 158 to the base plate 186 ofthe grounding deck 146. The mounting assembly 240 includes two clampsections 222A, 222B, the clamp ring 230, and the hardware 242. As shown,when the power tube 158 is operably positioned with respect to the clampsections 222A, 222B and the clamp ring 230, an outer edge 244 of thegrid terminal 216 is positioned under the clamp sections 222A, 222B. Thegrid terminal 216 is positioned on top of the base plate 186. The clampsections 222A, 222B are positioned on top of the clamp ring 230, and theclamp ring 230 extends around the hardware 242.

Accordingly, the grid terminal 216 may be held between the base plate186 and the clamp sections 222A, 222B. In some embodiments, the powertube 158 is permitted to have any rotational orientation with respect tothe central axis 205. More specifically, conventional power tubes mayrequire that thru-holes of the grid collar be aligned with correspondingholes of the base plate. In the illustrated embodiment, the thru-holesare not require to align with corresponding holes of the base plate 186,because the grid terminal 216 is compressed between the clamp sections222A, 222B and the base plate 186.

In the illustrated embodiment, the tuning capacitor assembly 204includes an output connector 202 having a connector wall 206 thatsurrounds a central axis 205 and defines a thru-hole 208 that receivesthe power tube 158. The output connector 202 is positioned on top of theanode terminal 214. The tuning capacitor assembly 204 also includes atuning sheet 209 that surrounds the central axis 205 and interfaces withthe connector wall 206. The tuning sheet 209 may be held against theconnector wall 206 using a fastener, such as a belt 207. The tuningcapacitor assembly 204 is described in greater detail in U.S.application Ser. No. 14/575,993, which is incorporated herein byreference in its entirety.

FIG. 9 is an exploded view of the capacitor assembly 250 formed inaccordance with an embodiment. The capacitor assembly 250 is configuredto be positioned within the input cavity 138 (FIG. 3) and provide anadded or external capacitance for an input circuit 295 (a portion ofwhich is shown in FIGS. 14, 15), which may function similar to aresonant circuit or tuned circuit. The input circuit may constitute theinput cavity resonator 390 and include the power tube 158 (FIG. 3), theinput inner conductor 162 (FIG. 3), an input outer conductor (notshown), and the capacitor assembly 250. The power tube 158 is configuredto resonate at a designated frequency that is based on a totalcapacitance of the input circuit and an inductance of the input circuit.The inductance is provided, at least in part, by the input innerconductor 162. The total capacitance is provided, at least in part, byan inherent capacitance (also called interelectrode capacitance) of thepower tube 158 and an external (or added) capacitance that is providedby the capacitor assembly 250. The external capacitance is in parallelto the inherent capacitance. In some embodiments, the externalcapacitance may permit a shorter input inner conductor 162. The externalcapacitance may be greater than or less than the inherent capacitance.In some embodiments, the capacitor assembly 250 may allow the tubeamplifier assembly 170 to be operated at 100 MHz or more.

In some embodiments, the external capacitance provided by the capacitorassembly 250 may reduce the likelihood of it being necessary to re-tunethe tube amplifier assembly 170 (or input circuit) after the power tube158 is replaced. During the lifetime operation of a tube amplifierassembly, it may be necessary to replace the used power tube with anewer power tube. Due to manufacturing tolerances, however, these powertubes may have different inherent capacitances. For example, the usedpower tube may have an inherent capacitance of 52 pico-Farad (pF), andthe new power tube may have an inherent capacitance of 48 pF. If thedifference in inherent capacitances is large enough, it may be necessaryto tune the input circuit after the used power tube is replaced with thenew power tube.

The capacitor assembly 250, however, reduces the likelihood that theinput circuit must be tuned. As described above, the capacitor assembly250 and the power tube 158 are in parallel such that the totalcapacitance of the input circuit is equal to the sum of the externalcapacitance and the inherent capacitance. Because the capacitor assembly250 is in parallel with the power tube 158, any change in the totalcapacitance is effectively reduced by the added external capacitance.Using the above examples of the new power tube and the used power tube,the change in capacitance of the input circuit without the capacitorassembly 250 would be about 8% ((52−48)/52)*100). The capacitor assembly250 would reduce the percent change in total capacitance. For example,assuming that the capacitor assembly 250 provides an externalcapacitance of 50 pF, the change in total capacitance of the inputcircuit with the capacitor assembly 250 would be about 4%((102−98)/102)*100).

In the illustrated embodiment, the capacitor assembly 250 includes aninsulation layer 252, an interposed (or pickup) plate 254, a pluralityof insulative spacers 258, a plurality of insulated support sleeves 259,a capacitive plate 260, and an adapter wall 262. The capacitive plate260 and the adapter wall 262 are coupled to each other to form a tubeadapter 264. In some embodiments, the capacitor assembly 250 may notinclude the adapter wall 262. Each of the insulation layer 252, theinterposed plate 254, the capacitive plate 260, and the adapter wall 262have or form a corresponding opening that aligns with the other openingsto form a tube passage 266 when the components are stacked together. Thetube passage 266 is sized and shaped to receive the power tube 158 (FIG.3).

The capacitor assembly 250 is configured to be coupled to the groundingdeck 146 (FIG. 3). As used herein, the term “coupled” may mean directlyor indirectly coupled. For example, a first component may be directlycoupled to a second component such that surfaces of the first and secondcomponents engage each other. A first component may be indirectlycoupled to a second component if the first and second components do notengage each other and, instead, an intervening component (or components)couples the first and second components to each other.

FIG. 10 is a plan view of the insulation layer 252. The insulation layer252 has an outer edge 268 that defines a perimeter of the insulationlayer 252 and an inner edge 270 that defines a layer opening 272. Thecentral axis 205 extends through a center of the layer opening 272. Theperimeter forms a circle having a center at the central axis 205 in theillustrated embodiment, but other shapes may be formed in alternativeembodiments. Also shown, the insulation layer 252 includes securingholes 274. The securing holes 274 are sized and shaped to receive thehardware 242 (FIG. 8) and are distributed around the central axis 205.Each of the securing holes 274 has a corresponding diameter 276.

FIG. 11 is a plan view of the interposed plate 254. The interposed plate254 has an outer edge 278 that defines a perimeter of the interposedplate 254 and an inner edge 280 that defines a plate opening 282. Thecentral axis 205 extends through a center of the plate opening 282. Theplate opening 282 may have an identical size and shape as the layeropening 272 (FIG. 10). The perimeter forms a circle having a center atthe central axis 205 in the illustrated embodiment.

Also shown, the interposed plate 254 includes securing holes 284. Thesecuring holes 284 are sized and shaped to receive the hardware 242(FIG. 8). The securing holes 284 are distributed around the central axis205 and positioned to align with the securing holes 274 (FIG. 10). Eachof the securing holes 284 has a corresponding diameter 286 that isdefined by a hole edge 287. The corresponding diameter 286 may begreater than the diameter 276 (FIG. 10) of the securing holes 274 (FIG.10). In an exemplary embodiment, the corresponding diameter 286 isconfigured such that a gap or spacing exists between the hole edge 287and the hardware 242.

FIG. 12 is an isolated perspective view of the tube adapter 264. Thecapacitive plate 260 has an outer edge 288 that defines a perimeter ofthe capacitive plate 260 and an inner edge 290 that defines a plateopening 292. The central axis 205 is configured to extend through acenter of the plate opening 292. The perimeter forms a circle having acenter at the central axis 205 in the illustrated embodiment. The shapeof the perimeter may be similar to the shape of the perimeter of theinterposed plate 254.

Also shown, the capacitive plate 260 includes securing holes 294. Thesecuring holes 294 are sized and shaped to receive the hardware 242(FIG. 8). The securing holes 294 are distributed around the central axis205 and positioned to align with the securing holes 274 (FIG. 10) andthe securing holes 284 (FIG. 11). Each of the securing holes 294 has acorresponding diameter 296 that is defined by a hole edge 297. Thecorresponding diameter 296 may be less than the diameter 286 (FIG. 11)of the securing holes 284. Optionally, the capacitive plate 260 has aplurality of openings 298 that are symmetrically distributed about thecentral axis 205. The openings 298 may be positioned, sized, and shapedto obtain a designated capacitance for the capacitor assembly 250.

The capacitor plate 260 may be secured to the adapter wall 262 using,for example, screws 302, but other fasteners may be used in alternativeembodiments. In an exemplary embodiment, the capacitive plate 260 isstamped from sheet metal, and the adapter wall 262 is formed from anon-conductive material. In other embodiments, however, the adapter wall262 may be formed from a conductive material. In other embodiments, thecapacitor plate 260 and the adapter wall 262 are part of a singleunitary part. For example, the capacitor plate 260 and the adapter wall262 may be molded from a common material.

FIG. 13 is cross-section of the tube adapter 264 through two of thescrews 302. As shown in FIGS. 12 and 13, the adapter wall 262 has aninner surface 304 that faces radially inward toward the central axis205. The adapter wall 262 also includes an outer surface 306 (FIG. 12)that faces radially away from the central axis 205. The tube adapter 264includes a plurality of flexible conductive elements 309 that areelectrically coupled to the capacitive plate 260. For example, theflexible conductive elements 309 may engage the capacitive plate 260 orbe electrically coupled to the capacitive plate 260 through the adapterwall 262.

The flexible conductive elements 309 may be electrically coupled to thecapacitive plate 260 and surround the tube passage 266. The flexibleconductive elements 309 may form a conductive frame 320 that surroundsand engages the power tube 158 (FIG. 3) when the power tube 158 isdisposed within the tube passage 266 (FIG. 9). The flexible conductiveelements 309 may be referred to as contact springs, spring fingers, orthe like. The flexible conductive elements 309 may be tightlydistributed around the central axis 205 such that a nominalcenter-to-center spacing between adjacent flexible conductive elements309 exists. Each of the flexible conductive elements 309 is shaped toengage the power tube 158 as the power tube 158 moves in a loadingdirection 310 that is parallel to the central axis 205. When movingalong the loading direction 310, the power tube 158 extends through theplate opening 282 before passing through into a tube opening 318 definedby the adapter wall 262. The plate opening 292 and the tube opening 318may combined to form an adapter opening of the tube adapter 264.

As shown in FIG. 13, each of the flexible conductive elements 309extends from a base 312 to a distal end 314. In an exemplary embodiment,the flexible conductive elements 309 are spring fingers that extend awayfrom the inner surface 304 of the adapter wall 262. The flexibleconductive elements 309 are shaped to engage the power tube 158 as thepower tube 158 is inserted into the tube passage 266. For example, eachof the flexible conductive elements 309 may have an inflection point 316that is closer to the central axis 205 (FIG. 12) than the inner surface304. When the power tube 158 engages the flexible conductive elements309, the flexible conductive elements 309 are deflected toward the innersurface 304. The flexible conductive elements 309 may electricallycouple the power tube 158 to the capacitive plate 260.

FIG. 14 is a cross-section of a portion of the input circuit 295 of thetube amplifier assembly 170. The base plate 186 has an output side 330and an input side 332 that face in opposite directions along the centralaxis 205. When the tube amplifier assembly 170 is fully constructed, theclamp sections 222A, 222B and the hardware 242 secure the grid terminal216 such that the grid terminal 216 is held between the clamp sections222A, 222B and the base plate 186. The pair of clamp sections 222A, 222Band each of the clamp ring 230, the grid terminal 216, the insulationlayer 252, the interposed plate 254, the insulative spacers 258, thecapacitive plate 260, the insulative support sleeves 259, and theadapter wall 262 are stacked with respect to each other along thecentral axis 205. Each bolt of the hardware 242 extends through one ofthe clamp sections 222A, 222B and the insulation layer 252, theinterposed plate 254, a corresponding insulative spacer 258, acorresponding insulated support sleeve 259, and the capacitive plate260. As such, the capacitor assembly 250 is secured to the base plate186 with each of the insulation layer 252, the interposed plate 254, andthe capacitive plate 260 extending parallel to the grounding deck 146 orthe base plate 186. In particular embodiments, the hardware 242 includesthreaded bolts (also referred to as studs or stud bolts) that aresecured to nuts at each end. The base plate 186 (or the grounding deck146) may include threaded holes. In such embodiments, the threaded holesmay hold the threaded bolts while the elements of the capacitor assembly250 are stacked relative to each other. Moreover, in this manner, it maybe possible to remove the power tube 158 without disassembling thecapacitor assembly 250 or the input resonator. For example, the nutsholding the clamp sections 222A, 222B may be removed thereby allowingthe clamp sections 222A, 222B and the power tube 158 to be removed.However, the threaded bolts may remain secured to the threaded holes.Accordingly, the capacitor assembly 250 may remain assembled and securedto the grounding deck 146.

The interposed plate 254 is positioned between the grounding deck 146and the capacitive plate 260. As shown, the interposed plate 254 iselectrically separated from the grounding deck 146 and the capacitiveplate 260. More specifically, the insulation layer 252 is disposedbetween the interposed plate 254 and the grounding deck 146, theinsulative spacers 258 are disposed between the interposed plate 254 andthe capacitive plate 260, and the insulated support sleeves 259 surrounda portion of the threaded bolts. In the illustrated embodiment, theinterposed plate 254 forms a part of the capacitor assembly 250. Theinterposed plate 254 may decrease an amount of capacitance provided bythe capacitor assembly 250. For example, the capacitor assembly 250 withthe electrically separated interposed plate 254 may be electricallysimilar to a pair of capacitors in series with respect to each other.

The grounding deck 146 (or the base plate 186) has a deck opening 334therethrough. The deck opening 334 is sized and shaped to permit thepower tube 158 to be inserted therethrough in the loading direction 310.The power tube 158 is configured to couple to the grounding deck 146 andbe positioned within the deck opening 334. The deck opening 334 isconfigured to align with the layer opening 272, the plate opening 282,the plate opening 292, and the tube opening 318 to form the tube passage266. The tube opening 318 and the plate opening 292 combine to form anadapter opening 319. For clarity, the layer opening 272 and the plateopening 282 are not referenced in FIG. 14. The tube passage 266 is sizedand shaped to receive the power tube 158. As shown, the cathode terminal212 is engaged to the flexible conductive elements 309 within the tubepassage 266.

The tube adapter 264 may be coupled to the grounding deck 146. The inputinner conductor 162 may include a coupling sheet 338. The coupling sheet338 may be, for example, a sheet of conductive material that wrapsaround the adapter wall 262. In some embodiments, an insulative film 341may be wrapped around the outer surface 306 of the adapter wall 262. Thecoupling sheet 338, in turn, is wrapped around the insulative film 341.As such, the insulative film 341 is positioned directly between thecoupling sheet 338 and the outer surface 306. The insulative film 341 isconfigured to DC-isolate the input inner conductor 162 from the tubeadapter 264. Also shown, the coupling sheet 338 defines a conductorpassage 340. The flexible leads 218, 220 extend through the conductorpassage 340 and couple to the decoupling capacitors 200 (FIG. 3).

FIG. 15 is a side view of an enlarged portion of the input circuit 295of the tube amplifier assembly 170. The coupling sheet 338 of the inputinner conductor 162 is secured to the tube adapter 264 using a belt 342.In the illustrated embodiment, the capacitor assembly 250 includes thecapacitive plate 260 of the tube adapter 264 and the interposed plate254. In other embodiments, however, the capacitor assembly 250 may onlyinclude the capacitive plate 260 without the interposed plate 254. Theinsulation layer 252 is not visible in FIG. 15. In other embodiments,the adapter wall 262 (FIG. 14) is not coupled to the capacitive plate260 or is not utilized by the tube amplifier assembly 170.

Also shown in FIG. 15, the tube amplifier assembly 170 includes firstand second communication lines 352, 354. The first communication line352 includes a conductive pathway, such as a thin strip of sheet metal,that is electrically coupled to the input cavity resonator 390 and isconfigured to provide an excitation signal thereto. The firstcommunication line 352 extends between the coupling sheet 338 and thestructure support 189.

The second communication line 354 includes a conductive pathway, such asa thin strip of sheet metal, that is electrically coupled to theinterposed plate 254. The second communication line 354 extends betweenthe interposed plate 254 and the structure support 190. During operationof the tube amplifier assembly 170, signals generated by the inputcavity resonator 390 may be detected by the interposed plate 254. Thesignals may be feedback signals that are indicative of an electricalperformance of the input cavity resonator 390. For example, the signalsfrom the interposed plate 254 may be used to calculate a load conditionof an output of the tube amplifier assembly 170. The signals may betransmitted through the communication line 354 to a control system (notshown) of the tube amplifier assembly 170 or the RF power generator 130.As a pickup device, the interposed plate 254 and capacitor assembly 250will function similar to a capacitive voltage divider without resonantbehavior that parasitic inductance may cause. Accordingly, the measuredwaveform shape may be preserved.

The capacitor assembly 250 with the interposed plate 254 may function asa capacitive divider of the cathode voltage directly at the cathodeterminal 212. In some embodiments, the interposed plate 254 may functionas a pickup device that detects signals from the input cavity resonator390. As described above, in particular embodiments, the capacitorassembly 250 and the power tube 158 are co-axial with respect to thecentral axis 205, and the capacitor assembly 250 is symmetrical (i.e.,circular or cylindrical) about the central axis 205 and the power tube158. In such embodiments, the coaxially-positioned and symmetricalcapacitor assembly 250 may have a low self-inductance that enables theinterposed plate 254 to detect measurements of high frequency signals(harmonics of the fundamental frequency) with low distortion. Moreover,the circular or cylindrical geometry of the capacitor assembly 250 mayallow the first and second communication lines 352, 354 to be coupled tothe capacitor assembly 250 at any rotational angle. In some embodiments,an impedance from the cathode terminal 212 to the grounding deck 146 atharmonics is corrected by the capacitor assembly 250 shaping thewaveform of the excitation signal to improve amplifier efficiency. Insome embodiments, the capacitor assembly 250 may have a low parasiticinductance and the cylindrical symmetry of the capacitor assembly 250may permit measurements of high frequency signals (harmonics of thefundamental frequency) with low distortion.

It is to be understood that the above description is intended to beillustrative, and not restrictive. For example, the above-describedembodiments (and/or aspects thereof) may be used in combination witheach other. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the inventivesubject matter without departing from its scope. Dimensions, types ofmaterials, orientations of the various components, and the number andpositions of the various components described herein are intended todefine parameters of certain embodiments, and are by no means limitingand are merely exemplary embodiments. Many other embodiments andmodifications within the spirit and scope of the claims will be apparentto those of skill in the art upon reviewing the above description. Thescope of the inventive subject matter should, therefore, be determinedwith reference to the appended claims, along with the full scope ofequivalents to which such claims are entitled. In the appended claims,the terms “including” and “in which” are used as the plain-Englishequivalents of the respective terms “comprising” and “wherein.”Moreover, in the following claims, the terms “first,” “second,” and“third,” etc. are used merely as labels, and are not intended to imposenumerical requirements on their objects. Further, the limitations of thefollowing claims are not written in means-plus-function format and arenot intended to be interpreted based on 35 U.S.C. §112(f) unless anduntil such claim limitations expressly use the phrase “means for”followed by a statement of function void of further structure.

This written description uses examples to disclose the variousembodiments, and also to enable a person having ordinary skill in theart to practice the various embodiments, including making and using anydevices or systems and performing any incorporated methods. Thepatentable scope of the various embodiments is defined by the claims,and may include other examples that occur to those skilled in the art.Such other examples are intended to be within the scope of the claims ifthe examples have structural elements that do not differ from theliteral language of the claims, or the examples include equivalentstructural elements with insubstantial differences from the literallanguages of the claims.

The foregoing description of certain embodiments of the presentinventive subject matter will be better understood when read inconjunction with the appended drawings. To the extent that the figuresillustrate diagrams of the functional blocks of various embodiments, thefunctional blocks are not necessarily indicative of the division betweenhardware circuitry. Thus, for example, one or more of the functionalblocks (for example, processors or memories) may be implemented in asingle piece of hardware (for example, a general purpose signalprocessor, microcontroller, random access memory, hard disk, or thelike). Similarly, the programs may be stand alone programs, may beincorporated as subroutines in an operating system, may be functions inan installed software package, or the like. The various embodiments arenot limited to the arrangements and instrumentality shown in thedrawings.

As used herein, an element or step recited in the singular and proceededwith the word “a” or “an” should be understood as not excluding pluralof said elements or steps, unless such exclusion is explicitly stated.Furthermore, references to “one embodiment” of the present invention arenot intended to be interpreted as excluding the existence of additionalembodiments that also incorporate the recited features. Moreover, unlessexplicitly stated to the contrary, embodiments “comprising,”“comprises,” “including,” “includes,” “having,” or “has” an element or aplurality of elements having a particular property may includeadditional such elements not having that property.

What is claimed is:
 1. A tube amplifier assembly comprising: a groundingdeck having a deck opening therethrough; a power tube coupled to thegrounding deck and positioned within the deck opening; and a tubeadapter coupled to the grounding deck, the tube adapter having acapacitive plate that extends parallel to the grounding deck and anadapter wall that is coupled to the capacitive plate, the tube adapterhaving an adapter opening that is aligned with the deck opening to forma tube passage, the tube adapter including flexible conductive elementsthat are electrically coupled to the capacitive plate and surround thetube passage, wherein the flexible conductive elements engage the powertube in the tube passage and electrically couple the power tube to thecapacitive plate, the grounding deck and the capacitive plate forming acapacitor assembly of the tube amplifier assembly.
 2. The tube amplifierassembly of claim 1, further comprising an interposed plate that extendsparallel to and is positioned between the grounding deck and thecapacitive plate, the interposed plate being electrically separated fromthe grounding deck and the capacitive plate, wherein the capacitiveplate, the interposed plate, and the grounding deck form the capacitorassembly of the tube amplifier assembly.
 3. The tube amplifier assemblyof claim 2, further comprising a communication line coupled to theinterposed plate, the communication line receiving signals from theinterposed plate that may be used to calculate a load condition.
 4. Thetube amplifier assembly of claim 1, further comprising an innerconductor that is coupled to the tube adapter, the inner conductorhaving a conductor passage that aligns with the tube passage.
 5. Thetube amplifier assembly of claim 4, wherein the power tube includesflexible leads that extend through the conductor passage.
 6. The tubeamplifier assembly of claim 1, wherein the power tube includes a gridcollar that engages the grounding deck.
 7. The tube amplifier assemblyof claim 1, wherein the flexible conductive elements are spring fingersthat extend away from an inner surface of the adapter wall, the springfingers being shaped to engage the power tube as the power tube isinserted into the tube passage.
 8. The tube amplifier assembly of claim1, wherein the capacitor assembly provides an external capacitance andthe power tube includes an inherent capacitance that form a totalcapacitance, the capacitor assembly reducing a percent change in thetotal capacitance when the power tube is replaced.
 9. A tube amplifierassembly comprising: a grounding deck having a deck openingtherethrough; a capacitive plate extending parallel to the groundingdeck; an interposed plate extending parallel to and positioned betweenthe grounding deck and the capacitive plate, the interposed plate beingelectrically separated from the grounding deck and the capacitive plate,wherein the capacitive plate has a plate opening and the interposedplate has a plate opening that are aligned with the deck opening to forma tube passage; and a power tube positioned within the tube passage andelectrically coupled to the capacitive plate, wherein the interposedplate, the capacitive plate, and the grounding deck form a capacitorassembly that is configured to provide capacitance of the tube amplifierassembly.
 10. The tube amplifier assembly of claim 9, further comprisinga communication line coupled to the interposed plate, the communicationline receiving signals from the interposed plate that may be used tocalculate a load condition.
 11. The tube amplifier assembly of claim 9,further comprising a tube adapter that is coupled to the grounding deck,the tube adapter including the capacitive plate and an adapter wall thatis coupled to the capacitive plate, the tube adapter having an adapteropening that is aligned with the deck opening to form the tube passage,the tube adapter including flexible conductive elements that surroundthe power tube, the flexible conductive elements engaging the power tubeand electrically coupling the power tube to the capacitive plate. 12.The tube amplifier assembly of claim 9, wherein the power tube includesflexible leads.
 13. The tube amplifier assembly of claim 9, wherein thecapacitor assembly provides an external capacitance and the power tubeincludes an inherent capacitance, the capacitor assembly reducing apercent change in the total capacitance when the power tube is replaced.